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Figure 392 Schematic diagram for SP queuing
A typical switch provides eight queues per port. As shown in Figure 392, SP queuing classifies eight
queues on a port into eight classes, numbered 7 to 0 in descending priority order.
SP queuing schedules the eight queues strictly according to the descending order of priority. It sends
packets in the queue with the highest priority first. When the queue with the highest priority is empty, it
sends packets in the queue with the second highest priority, and so on. You can assign mission-critical
packets to the high priority queue to ensure that they are always served first and common service (such
as Email) packets to the low priority queues to be transmitted when the high priority queues are empty.
The disadvantage of SP queuing is that packets in the lower priority queues cannot be transmitted if there
are packets in the higher priority queues. This may cause lower priority traffic to starve to death.
WRR queuing
WRR queuing schedules all the queues in turn to ensure that every queue can be served for a certain time,
as shown in Figure 393.
Figure 393 Schematic diagram for WRR queuing
A typical switch provides eight output queues per port. WRR assigns each queue a weight value
(represented by w7, w6, w5, w4, w3, w2, w1, or w0) to decide the proportion of resources assigned to
the queue. On a 100 Mbps port, you can set the weight values of WRR queuing to 50, 30, 10, 10, 50,
30, 10, and 10 (corresponding to w7, w6, w5, w4, w3, w2, w1, and w0 respectively). In this way, the
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